Carriers or boats for holding a plurality of spaced apart semiconductor products, such as wafers, green sheets, ceramic substrates, glass and/or metal masks, or rigid or floppy or optical disks, to name a few, are employed in many types of semiconductor processing systems to facilitate batch processing and to minimize damage of the products due to improper handling. Such carriers are employed, for example, as input magazines for sequentially supplying semiconductor products to automatic product handling and processing systems, or as output magazines for sequentially receiving processed semiconductor products from such systems, or as intermediate (throughput) devices for holding semiconductor products that may require sampling, testing, or some other special handling at some point during processing by such systems. In nearly all of these cases the product carriers must, at some point, be manually transported to or from such systems with the attendant risk that in so doing the semiconductor products may slip from the product carriers and thereby be damaged or broken, or that the product carrier may not be strong enough to hold all the products. This risk is particularly great in the case of carriers of the type permitting unobstructed passage of semiconductor products therethrough. If such carriers are tilted forward or backward while they are being manually transported, any semiconductor product contained therein may slide out. Although this risk is much less critical in the case of carriers of the type permitting passage of semiconductive wafers into or out of the carriers from only one end of the carrier, care must still be exercised while such a carrier is being manually transported to avoid tilting.
Another problem associated with a product carrier is deformation of the carrier. Past efforts to eliminate the risk of a carrier deforming during manually transporting semiconductor products have resulted in elaborate procedures. The risk was, in fact, not reduced at all because most all of these elaborate procedures address how the operator should transport these products in the carrier, without designing a carrier that would be versatile for all operations. Moreover, when placing the carrier in a wafer handling and processing system, the person transporting the carrier also had to remember to carefully release the semiconductor products into the handling and processing system. In addition to these drawbacks, such mechanisms are generally complex and add significantly to the cost of the carrier.
In an effort to reduce direct labor assembly costs, many manufacturers are presently employing robots for inserting the products into the appropriate location within electronic devices or testing or assembly devices. In order for a robot to successfully accomplish its task, the control system must be programmed to know both the precise location from which the product is to be picked up, i.e., the storage location, and the location at which the product is to be deposited. The versatile product carrier of this invention has means to indicate to the robot the precise location from where the product can be picked up or in which slot the product has to be placed.
Products are often transported in slotted plastic boxes in which they are held in edgewise fashion, and it is desirable to have the robot pick them up directly from the box. The plastic side-walls of conventional boxes are not always precise because of manufacturing tolerances, or the plastic side-walls may tend to become distorted after extended use. As a result, the location of the products within the box may not be precise or may tend to shift. The actual location of the product to be inserted into the box or taken out of the box by the robot may then differ from the location of the product known to the robot control system so that the robot may not properly grasp the desired product or may even grasp a different product from that which it has been commanded to grasp. This is a particular problem where a series of boxes must be handled and it is important to avoid inconsistencies from box to box.
In an effort to overcome these and other disadvantages associated with the storage and transportation of the products within a plastic box, the present invention is specifically directed to a structurally integrated product carrier which is directly engageable by a locating device, for precisely locating the products to facilitate automated handling.
More would be involved in highly automated systems. Obviously these product carriers require a considerable amount of handling.
The product carrier of the present invention greatly simplifies the handling of the empty carriers. In addition, the design of the product carrier permits the carriers to be stacked compactly and stored on site without substantially increasing the required floor space. The carrier can also be stored in an unassembled state to save valuable storage or site space. After processing, the empty product carriers are returned to the designated site so that additional product may be placed into the carrier.
These types of carriers or boats are used by the thousands in the semiconductor industry, and therefore, one of the major concerns for such product carriers or cassettes is their low cost along with other concerns.
The invention is a "Versatile Product Carrier", or VPC. Basically, the product carrier has two end plates and two cross-bars. The two end plates have to be symmetrical and the two cross-bars should be symmetrical with respect to each other. The exact shape of the two cross-bars will depend upon the product shape or geometry. The end plates have a centerpiece, and the centerpiece has columns at each end. These columns have openings on the side to accommodate the retaining end of the cross-bars. The centerpiece also has wave-like tracks for minimum point contact and to vertically hold the product. The minimum point contact further reduces particulate contamination normally produced by rubbing of the surfaces or by the adherence of the particulates to the surface within the track. The tracks in the centerpiece also keep the product from sliding or being damaged while it is being transported. Instead of the wave-like tracks in the centerpiece one could have slots that are presently used in the industry. The slots of course do not provide the minimum point contact. Stops in the centerpiece prevents the product from slipping or sliding through the product carriers.
The length of the cross-bars can vary depending on the size and/or shape of the product. Similarly, the size of the end plate and/or the opening or slots between the wave-like tracks or guides in the end piece can also vary depending upon the size of the product. These product carriers can be stacked one on top of each other and can be orientated as desired.
The material used to make the parts for the product carriers or cassettes should be of a strength to withstand some of the process that the product carrier either alone or with the substrates are normally exposed to, such as, spinning, developing, cleaning, baking, transferring, automatic inspection, and other loading and unloading operations.
The versatile product carrier of this invention is primarily made using extruded or molded plastic, but other types of material can be used, such as composites and metals. The preferable metals, for example, could be aluminum or stainless steel. Similarly, the product carrier can also be made from cast or machined plastic or metal or ceramic or any other material that would suit the process and/or product requirements. A portion or different parts or the whole versatile product carrier could also be coated with a coating of a suitable material. The suitable materials, for example, could be polytetrafluoroethylene or perfluoro alkoxy alkaline, to name a few. The overcoating or coating of the parts or the whole product carrier has many advantages, such as, to reduce or provide resistance from attack by chemicals and/or fluids. In situations where the part is made from a porous material, this overcoating would reduce or eliminate absorption of fluids and/or liquid by the porous part. Another advantage of having a coating would be to provide a cushion or abrasion-resistance to the product that may come in contact with the part. The propensity of the product carrier made of non-metallic material or having such an overcoating to damage the product contained therein is less than that of a product carrier made of aluminum or other metals. An antistatic coating could also be applied onto at least a part or a portion of the product carrier.
The material and design that is chosen to make the product carrier could also take into account the optimum chemical-mechanical-temperature compatibility for applications where the product carrier along with the product is going to be immersed into a liquid solution or a bath. Similarly, the criteria could also include whether or not the product carrier will be used in a clean room or a contamination-free environment.
The product carrier of this invention with minor changes can accept new products having different sizes. This means that all product carriers, both new and old, will be common to all existing process tools and handling techniques, e.g., robots, auto handling, monitors, readers, etc. All the product carriers will have the same form factor, e.g., foot print. Different products can be moved in and out of the production line with little or no changes. Similarly, the production line does not have to change.